Method of manufacturing solventless multilayered electrodes

ABSTRACT

A method for manufacturing a solventless multilayered electrode may include mixing electrode particles with binders to form dry electrode mixtures, compressing the dry electrode mixtures to form electrode films, stacking the electrode films, and compressing the stacked electrode films. Suitable electrode films may include active material particles, conductive particles, electrochemically inactive ceramic particles, and/or the like. In some examples, compressing the stacked electrode films may include compressing the electrode films between pairs of rollers having patterns disposed on one or more exterior surfaces, thereby increasing surface roughness of the electrode films. A system for manufacturing solventless multilayered electrodes may comprise a first plurality of rollers configured to compress dry electrode mixes into electrode films, and a second plurality of rollers configured to compress a stack of electrode films into a single electrode stack.

CROSS-REFERENCES

The following applications and materials are incorporated herein, intheir entireties, for all purposes: U.S. Provisional Patent ApplicationSer. No. 63/116,645, filed Nov. 20, 2020; U.S. patent application Ser.No. 17/459,378, filed Aug. 27, 2021.

FIELD

This disclosure relates to systems and methods for electrodes andelectrochemical cells. More specifically, the disclosed embodimentsrelate to methods of manufacturing solventless multilayered electrodes.

INTRODUCTION

Environmentally friendly sources of energy have become increasinglycritical, as fossil fuel-dependency becomes less desirable. Mostnon-fossil fuel energy sources, such as solar power, wind, and the like,require some sort of energy storage component to maximize usefulness.Accordingly, battery technology has become an important aspect of thefuture of energy production and distribution. Most pertinent to thepresent disclosure, the demand for secondary (i.e., rechargeable)batteries has increased. Various combinations of electrode materials andelectrolytes are used in these types of batteries, such as lead acid,nickel cadmium (NiCad), nickel metal hydride (NiMH), nickel manganesecobalt oxide (NMC), nickel cobalt aluminum oxide (NCA), lithium ion(Li-ion), and lithium-ion polymer (Li-ion polymer). Solvents commonlyused in manufacturing processes for electrodes and electrochemical cellsare expensive and may be harmful to the environment.

SUMMARY

The present disclosure provides systems, apparatuses, and methodsrelating to solventless multilayered electrodes.

In some embodiments, a solventless method for manufacturing an electrodeincludes: compressing a first dry electrode mixture between a first pairof rollers to form a first standalone electrode film, wherein a firstroller of the first pair of rollers includes a pattern disposed on anexternal surface; increasing a surface roughness of a first surface ofthe first standalone electrode film using the first patterned roller ofthe first pair of rollers; compressing a second dry electrode mixturebetween a second pair of rollers to form a second standalone electrodefilm, wherein a second roller of the second pair of rollers includes apattern disposed on an external surface; increasing a surface roughnessof a second surface of the second standalone electrode film using thesecond patterned roller of the second pair of rollers; stacking thefirst standalone electrode film onto a current collector; stacking thesecond standalone electrode film onto the first standalone electrodefilm, such that the first surface of the first standalone electrode filmis adjacent to the second surface of the second standalone electrodefilm; and compressing the stacked electrode films such thatinterpenetrating boundary structures form between the first standaloneelectrode film and the second standalone electrode film.

In some embodiments, an electrode for an electrochemical cell comprises:a current collector substrate; a first active material layer layeredonto the current collector substrate, the first active material layercomprising a first stand-alone electrode film including a plurality offirst active material particles adhered together by a first bindermixture; and a second active material layer layered onto the firstactive material layer, the second active material layer comprising asecond stand-alone electrode film including a plurality of second activematerial particles adhered together by a second binder mixture; whereinthe first active material particles are encapsulated in a polymer matrixformed by the first binder mixture and the second active materialparticles are encapsulated in a polymer matrix formed by the secondbinder mixture.

In some embodiments, a system for solventless manufacturing ofelectrodes includes: a plurality of first pairs of rollers configured tocompress dry electrode mixtures comprising particulate into stand-aloneelectrode films; a hopper configured to pour the dry electrode mixturesinto a space between each of the first pairs of rollers; and a secondpair of rollers configured to compress a stack of stand-alone electrodefilms into a single electrode stack.

Features, functions, and advantages may be achieved independently invarious embodiments of the present disclosure, or may be combined in yetother embodiments, further details of which can be seen with referenceto the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative electrochemical cell in accordance withaspects of the present disclosure.

FIG. 2 is a flow chart depicting steps of an illustrative method formanufacturing solventless multilayered electrodes.

FIG. 3 is a schematic view of an illustrative manufacturing system forsolventless multilayered electrodes in accordance with aspects of thepresent disclosure.

FIG. 4 is a schematic view of a first set of rollers for use with themanufacturing system of FIG. 3.

FIG. 5 is a schematic view of a second set of rollers for use with themanufacturing system of FIG. 3.

FIG. 6 is a schematic view of illustrative solventless multilayeredelectrodes in accordance with aspects of the present disclosure.

FIG. 7 is a schematic view of illustrative solventless multilayeredelectrodes including conductive carbon layers.

FIG. 8 is a schematic view of an illustrative solventless multilayeredelectrodes including conductive carbon layers and integrated ceramicseparator layers.

FIG. 9 is a schematic view of illustrative solventless electrodesincluding conductive carbon layers and roughened layer interfaces inaccordance with aspects of the present disclosure.

FIG. 10 is a schematic view of illustrative solventless multilayeredelectrodes including conductive carbon layers, integrated ceramicseparator layers, and roughened layer interfaces in accordance withaspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects and examples of solventless multilayered electrodes, aswell as related methods, are described below and illustrated in theassociated drawings. Unless otherwise specified, a solventlessmultilayered electrode in accordance with the present teachings, and/orits various components, may contain at least one of the structures,components, functionalities, and/or variations described, illustrated,and/or incorporated herein. Furthermore, unless specifically excluded,the process steps, structures, components, functionalities, and/orvariations described, illustrated, and/or incorporated herein inconnection with the present teachings may be included in other similardevices and methods, including being interchangeable between disclosedembodiments. The following description of various examples is merelyillustrative in nature and is in no way intended to limit thedisclosure, its application, or uses. Additionally, the advantagesprovided by the examples and embodiments described below areillustrative in nature and not all examples and embodiments provide thesame advantages or the same degree of advantages.

This Detailed Description includes the following sections, which followimmediately below: (1) Definitions; (2) Overview; (3) Examples,Components, and Alternatives; (4) Advantages, Features, and Benefits;and (5) Conclusion. The Examples, Components, and Alternatives sectionis further divided into subsections, each of which is labeledaccordingly.

Definitions

The following definitions apply herein, unless otherwise indicated.

“Comprising,” “including,” and “having” (and conjugations thereof) areused interchangeably to mean including but not necessarily limited to,and are open-ended terms not intended to exclude additional, unrecitedelements or method steps.

Terms such as “first”, “second”, and “third” are used to distinguish oridentify various members of a group, or the like, and are not intendedto show serial or numerical limitation.

“AKA” means “also known as,” and may be used to indicate an alternativeor corresponding term for a given element or elements.

“Coupled” means connected, either permanently or releasably, whetherdirectly or indirectly through intervening components.

Directional terms such as “up,” “down,” “vertical,” “horizontal,” andthe like should be understood in the context of the particular object inquestion. For example, an object may be oriented around defined X, Y,and Z axes. In those examples, the X-Y plane will define horizontal,with up being defined as the positive Z direction and down being definedas the negative Z direction.

“Providing,” in the context of a method, may include receiving,obtaining, purchasing, manufacturing, generating, processing,preprocessing, and/or the like, such that the object or materialprovided is in a state and configuration for other steps to be carriedout. “PTFE” is polytetrafluorethylene.

“PVDF” is polyvinylidene fluoride.

“PE” is polyethylene.

“PP” is polypropylene.

“PEO” is polyethylene oxide.

“SBR” is steryl butadiene rubber.

“NMP” is n-methyl-2-pyrrolidone.

In this disclosure, one or more publications, patents, and/or patentapplications may be incorporated by reference. However, such material isonly incorporated to the extent that no conflict exists between theincorporated material and the statements and drawings set forth herein.In the event of any such conflict, including any conflict interminology, the present disclosure is controlling.

Overview

Solventless multilayered electrodes and electrochemical cells generallyinclude electrode layers formed from a dry powder or other dry mixtureof electrode materials, which are then compressed to form electrodelayers. In contrast, conventional electrochemical cells are generallymanufactured by layering one or more slurries onto a current collectorcomprising a metal foil and/or other suitable substrate. Slurriesutilized in conventional electrochemical cells generally comprise amixture of suitable electrode materials, such as active materialparticles, binders, conductive additives, and/or the like, adheredtogether and/or solvated by a solvent. Manufacturing processes utilizingelectrode slurries typically require that electrodes be dried at one ormore periods during manufacture, significantly increasing manufacturingtime. Additionally, solvents utilized in conventional electrodemanufacturing processes may be costly and/or harmful to the environmentif not recovered, and manufacturing facilities therefore include solventrecovery systems, increasing cost of production and potential hazards toworkers and to the environment.

In contrast, solventless electrodes and electrochemical cells aremanufactured from dry mixtures of electrode materials. These drymixtures include active materials, binders, and any suitable additivessuch as conductive additives. In some examples, individual mixtures ofdry electrode materials are compressed (e.g., calendered, rolled, etc.)to form stand-alone electrode films. The stand-alone electrode films arelayered and/or stacked and compressed further to produce a multilayereddry electrode structure. In some examples, electrode films disposedclosest to the current collector are laminated (e.g., adhered, heated,and/or cured) onto the current collector after being compressed. In someexamples, electrode materials disposed closest to the current collectorare compressed onto the current collector, thereby forming a film aroundor on one side of the current collector.

In some examples, dry electrode mixtures include any and/or all of:active material particles, conductive additives, ceramic particlesand/or the like, which are collectively mixed with binders. In someexamples, multilayered solventless electrodes include stacked layers ofelectrode films, each comprising a different dry electrode mixture.Exemplary dry electrode mixtures may comprise any suitable combinationof electrode components, such as: active material particles, conductiveadditives, and binders; ceramic particles and binders; conductiveadditives and binders; and/or the like.

Solventless multilayered electrodes may be anodes or cathodes. Inexamples where the solventless multilayered electrodes are anodes,active material particles included in the dry electrode mixtures maycomprise any suitable anode material or combination of anode materials,such as graphite (artificial or natural), hard carbon, titanate,titania, transition metals in general, elements in group 14 (e.g.,carbon, silicon, tin, germanium, etc.), oxides, sulfides, transitionmetals, halides, chalcogenides, and/or the like. In examples where thesolventless multilayered electrodes are cathodes, active materialparticles included in the dry electrode mixtures may comprise anysuitable cathode material or combination of cathode materials, such astransition metals (for example, nickel, cobalt, manganese, copper, zinc,vanadium, chromium, iron), and their oxides, phosphates, phosphites,silicates, alkalines and alkaline earth metals, aluminum, aluminumoxides and aluminum phosphates, halides, chalcogenides, and/or the like.In some examples, solventless multilayered electrodes include multipleactive material layers including active material particles. In theseexamples, each active material layer may include a different activematerial or mixture of active material particles.

Binders included in dry electrode mixtures according to aspects of thepresent disclosure may comprise any suitable material for use in dryelectrode processing, such as polytetrafluorethylene (PTFE); polyolefinssuch as polyvinylidene difluoride (PVDF), polyethylene (PE),polypropylene (PP) polyethylene oxide (PEO), and/or their mixtures orcopolymers; steryl butadiene rubber (SBR); polyacrylic acid; polyvinylalcohol; carboxymethyl cellulose; and/or the like. In some examples, thedry electrode mixtures include binder mixtures comprising a plurality ofbinders. Exemplary binder mixtures include PTFE mixed with PVDF; PTFEmixed with co-polymers of PVDF, PTFE mixed with PEO; PTFE mixed with PP;and/or the like.

Dry electrode mixtures described above may additionally includeconductive additives, which may include any suitable particlesconfigured to increase electrical conductivity within the electrode,such as nanometer-sized carbon (e.g., carbon black and/or graphite);ketjen black; a graphitic carbon; a low dimensional carbon (e.g., carbonnanotubes); a carbon fiber; and/or the like.

In some examples, solventless multilayered electrodes include one ormore non-active layers configured to improve electrical properties andelectrode stability. These non-active layers do not include activematerial particles, but may include conductive carbon particles and/orelectrochemically inactive and electrically non-conductive inorganicparticles mixed with binder mixtures.

A first illustrative non-active layer includes conductive carbonparticles, such as nanometer-sized carbon (e.g., carbon black and/orgraphite); ketjen black; a graphitic carbon; a low dimensional carbon(e.g., carbon nanotubes); a carbon fiber; and/or the like, mixed withany suitable binder material and/or any mixture thereof, such aspolytetrafluorethylene (PTFE); polyolefins such as polyvinylidenefluoride (PVDF), polyethylene (PE), polypropylene (PP) and/or theirmixtures or copolymers; polyethylene oxide (PEO); steryl butadienerubber (SBR); polyacrylic acid; polyvinyl alcohol; carboxymethylcellulose; and/or the like. This first exemplary non-active layer (AKAcarbon conductive layer) may be disposed between a bottom surface of anelectrode active material layer and a top surface of a currentcollector, and may be configured to increase electrical conductivitybetween the active material layers and the current collector.

A second illustrative non-active layer includes electrochemicallyinactive (AKA non-active) ceramic particles comprising any suitableceramic materials such as aluminum oxide (i.e., alumina (α-Al₂O₃)),corundum, calcined, tabular, synthetic boehmite, silicon oxides orsilica, zirconia, and/or the like, mixed with any suitable bindermaterial and/or any mixture thereof, such as polytetrafluorethylene(PTFE); polyolefins such as polyvinylidene fluoride (PVDF), polyethylene(PE), polypropylene (PP) and/or their mixtures or copolymers;polyethylene oxide (PEO); steryl butadiene rubber (SBR); polyacrylicacid; polyvinyl alcohol; carboxymethyl cellulose; and/or the like. Insome examples, the ceramic particles are electrically non-conductive.This second exemplary non-active layer (AKA separator layer) may bedisposed adjacent a top surface of an electrode active material layer,and may be configured such that the separator isolates the electrode(e.g., anode or cathode) from an adjacent electrode included within theelectrochemical cell, while maintaining permeability to a charge carriersuch as a lithium-ion containing electrolyte.

An illustrative method for manufacturing multilayered solventlesselectrodes includes mixing electrode materials to form dry electrodemixes; compressing individual electrode mixes to form electrode films;heating the electrode films; stacking the electrode films; compressingthe stacked films; and heating the compressed electrode stack.

A manufacturing system for manufacturing multilayered solventlesselectrodes includes a first plurality of heated rollers configured tocompress a first plurality of dry electrode mixes to form a firstplurality of electrode films and a second set of heated rollersconfigured to compress a stack of electrode films to form a multilayeredsolventless electrode stack. In some examples, certain rollers of thefirst plurality of heated rollers include patterns disposed on externalsurfaces, the patterns configured to increase a surface roughness ofelectrode films formed using the rollers. In some examples, themanufacturing system includes a heater configured to heat a currentcollector configured to be utilized in the multilayered solventlesselectrode. In some examples, the heater is configured to laminate abottom (AKA first) electrode layer onto the current collector, therebyincreasing adhesion.

Examples, Components, and Alternatives

The following sections describe selected aspects of illustrativesolventless multilayered electrodes as well as related systems and/ormethods. The examples in these sections are intended for illustrationand should not be interpreted as limiting the scope of the presentdisclosure. Each section may include one or more distinct embodiments orexamples, and/or contextual or related information, function, and/orstructure.

A. Illustrative Electrochemical Cell

This section describes an illustrative electrochemical cell includingelectrodes according to the present teachings. The electrochemical cellmay include any bipolar electrochemical device, such as a battery (e.g.,lithium-ion battery, secondary battery).

Referring now to FIG. 1, an electrochemical cell 100 is illustratedschematically in the form of a lithium-ion battery. Electrochemical cell100 includes a positive and a negative electrode, namely a cathode 102and an anode 104. The cathode and anode are sandwiched between a pair ofcurrent collectors 106, 108, which may comprise metal foils and/or othersuitable substrates. Current collector 106 is electrically coupled tocathode 102, and current collector 108 is electrically coupled to anode104. The current collectors enable the flow of electrons, and therebyelectrical current, into and out of each electrode. An electrolyte 110disposed throughout the electrodes enables the transport of ions betweencathode 102 and anode 104. In the present example, electrolyte 110includes a liquid solvent and a solute of dissolved ions. Electrolyte110 facilitates an ionic connection between cathode 102 and anode 104.

Electrolyte 110 is assisted by a separator 112, which physicallypartitions the space between cathode 102 and anode 104. Separator 112 isliquid-permeable, and enables the movement (flow) of ions withinelectrolyte 110 and between the two electrodes. In some embodiments,electrolyte 110 includes a polymer gel and/or solid ion conductor,augmenting and/or replacing (and performing the function of) separator112.

Cathode 102 and anode 104 are composite structures, which compriseactive material particles, binders, conductive additives, and pores(void space) into which electrolyte 110 may penetrate. An arrangement ofthe constituent parts of an electrode is referred to as amicrostructure, and/or more specifically, an electrode microstructure.

The binder may comprise any suitable material configured to adhereactive material particles, binders, and other electrode components intoa stand-alone electrode film. In some examples, the binder includes apolyolefin or other non-fibrilizable polymer, such as polyvinylidenedifluoride (PVDF), polyethylene (PE), polypropylene (PP), and/or theirmixtures or copolymers. In some examples, the binder includes afibrilizable polymer, such as polytetrafluoroethylene (PTFE) and/or thelike. In some examples, the binder includes polyethylene oxide (PEO);steryl butadiene rubber (SBR); polyacrylic acid; polyvinyl alcohol;carboxymethyl cellulose; and/or the like. In some examples, the binderincludes a mixture of one or more non-fibrilizable polymers and one ormore fibrilizable polymers, such as PTFE mixed with PVDF; PTFE mixedwith co-polymers of PVDF, PTFE mixed with PEO; and PTFE mixed with PP.

The conductive additives may include any suitable material configured toconduct within the electrode, such as nanometer-sized carbon (e.g.,carbon black and/or graphite); ketjen black; a graphitic carbon; a lowdimensional carbon (e.g., carbon nanotubes); a carbon fiber; and/or thelike.

In some examples, the chemistry of the active material particles differsbetween cathode 102 and anode 104. For example, anode 104 may includegraphite (artificial or natural), hard carbon, titanate, titania,transition metals in general, elements in group 14 (e.g., carbon,silicon, tin, germanium, etc.), oxides, sulfides, transition metals,halides, and/or chalcogenides. On the other hand, cathode 102 mayinclude transition metals (for example, nickel, cobalt, manganese,copper, zinc, vanadium, chromium, iron), and their oxides, phosphates,phosphites, and/or silicates. The cathode may include alkalines andalkaline earth metals, aluminum, aluminum oxides and aluminumphosphates, as well as halides and/or chalcogenides. In anelectrochemical device, active materials participate in anelectrochemical reaction or process with a working ion to store orrelease energy. For example, in a lithium-ion battery, the working ionsare lithium ions.

Electrochemical cell 100 may include packaging (not shown). For example,packaging (e.g., a prismatic can, stainless steel tube, polymer pouch,etc.) may be utilized to constrain and position cathode 102, anode 104,current collectors 106 and 108, electrolyte 110, and separator 112.

For electrochemical cell 100 to properly function as a secondarybattery, active material particles in both cathode 102 and anode 104must be capable of storing and releasing lithium ions through therespective processes known as lithiating and delithiating. Some activematerials (e.g., layered oxide materials or graphitic carbon) fulfillthis function by intercalating lithium ions between crystal layers.Other active materials may have alternative lithiating and delithiatingmechanisms (e.g., alloying, conversion).

When electrochemical cell 100 is being charged, anode 104 acceptslithium ions while cathode 102 donates lithium ions. When a cell isbeing discharged, anode 104 donates lithium ions while cathode 102accepts lithium ions. Each composite electrode (i.e., cathode 102 andanode 104) has a rate at which it donates or accepts lithium ions thatdepends upon properties extrinsic to the electrode (e.g., the currentpassed through each electrode, the conductivity of the electrolyte 110)as well as properties intrinsic to the electrode (e.g., the solid statediffusion constant of the active material particles in the electrode;the electrode microstructure or tortuosity; the charge transfer rate atwhich lithium ions move from being solvated in the electrolyte to beingintercalated in the active material particles of the electrode; etc).

During either mode of operation (charging or discharging) anode 104 orcathode 102 may donate or accept lithium ions at a limiting rate, whererate is defined as lithium ions per unit time, per unit current. Forexample, during charging, anode 104 may accept lithium at a first rate,and cathode 102 may donate lithium at a second rate. When the secondrate is lesser than the first rate, the second rate of the cathode wouldbe a limiting rate. In some examples, the differences in rates may be sodramatic as to limit the overall performance of the lithium-ion battery(e.g., cell 100). Reasons for the differences in rates may depend on anenergy required to lithiate or delithiate a quantity of lithium-ions permass of active material particles; a solid-state diffusion coefficientof lithium ions in an active material particle; and/or a particle sizedistribution of active material within a composite electrode. In someexamples, additional or alternative factors may contribute to theelectrode microstructure and affect these rates.

B. Illustrative Method for Manufacturing Multilayered SolventlessElectrodes

This section describes steps of an illustrative method 200 formanufacturing multilayered solventless electrodes; see FIG. 2. Aspectsof electrochemical cells described above may be utilized in the methodsteps described below. Where appropriate, reference may be made tocomponents and systems that may be used in carrying out each step. Thesereferences are for illustration, and are not intended to limit thepossible ways of carrying out any particular step of the method.

FIG. 2 is a flowchart illustrating steps performed in an illustrativemethod, and may not recite the complete process or all steps of themethod. Although various steps of method 200 are described below anddepicted in FIG. 200, the steps need not necessarily all be performed,and in some cases may be performed simultaneously or in a differentorder than the order shown.

Step 202 of method 200 includes mixing electrode materials to form aplurality of dry electrode mixtures (AKA dry electrode mixes). Dryelectrode mixtures utilized to form multilayered solventless electrodesfor electrochemical cells (such as electrochemical cell 100) include aplurality of electrode materials such as active material particles,binders, conductive additives, non-active ceramic particles, and/or thelike. Not all electrode mixtures include all possible electrodematerials, and not all electrodes include all possible electrodematerials.

Dry electrode mixtures included in multilayered solventless electrodesgenerally include a plurality of non-binder electrode materials adheredtogether by one or more binders. Mixing electrode materials to form dryelectrode mixes includes mixing a unique dry electrode mix for eachdesired layer of a multilayered solventless electrode.

In some examples, a multilayered solventless electrode includes a firstactive material layer and a second active material layer. Mixingelectrode materials to form dry electrode mixes therefore includes:forming a first dry electrode mix including a plurality of first activematerial particles and a first binder mixture and forming a second dryelectrode mix including a plurality of second active material particlesand a second binder mixture. In some examples, the first and second dryelectrode mixes include conductive additives.

In some examples, a multilayered solventless electrode includes a firstactive material layer, a second active material layer, and a carbonconductive layer. Mixing electrode materials to form dry electrode mixestherefore includes: forming a first dry electrode mix including aplurality of first active material particles and a first binder mixture,forming a second dry electrode mix including a plurality of secondactive material particles and a second binder mixture, and forming athird dry electrode mix including a plurality of electrically conductivecarbon particles and a third binder mixture. In some examples, the firstand second dry electrode mixes include conductive additives.

In some examples, a multilayered solventless electrode includes a firstactive material layer, a second active material layer, a separatorlayer, and a carbon conductive layer. Mixing electrode materials to formdry electrode mixes therefore includes: forming a first dry electrodemix including a plurality of first active material particles and a firstbinder mixture, forming a second dry electrode mix including a pluralityof second active material particles and a second binder mixture, forminga third dry electrode mix including a plurality of electricallyconductive carbon particles and a third binder mixture, and forming afourth dry electrode mix including a plurality of non-active ceramicparticles and a fourth binder mixture. In some examples, the first andsecond dry electrode mixes include conductive additives.

In some examples, the multilayered solventless electrode is an anode,and the first and second active material particles comprise any suitableanode material or combination of anode materials, such as graphite(artificial or natural), hard carbon, titanate, titania, transitionmetals in general, elements in group 14 (e.g., carbon, silicon, tin,germanium, etc.), oxides, sulfides, transition metals, halides,chalcogenides, and/or the like. In some examples, the multilayeredsolventless electrode is a cathode, and the first and second activematerial particles comprise any suitable cathode material or combinationof cathode materials, such as transition metals (for example, nickel,cobalt, manganese, copper, zinc, vanadium, chromium, iron), and theiroxides, phosphates, phosphites, silicates, alkalines and alkaline earthmetals, aluminum, aluminum oxides and aluminum phosphates, halides,chalcogenides, and/or the like. In some examples, the first activematerial particles and the second active material particles comprisedifferent active materials. In some examples, the first active materialparticles and the second active material particles comprise activematerial particles having different particle shapes and/or sizes.

Conductive carbon particles utilized in carbon conductive layers maycomprise any suitable carbon-based material configured to increaseelectrical conductivity between active material layers and the currentcollector, such as nanometer-sized carbon (e.g., carbon black and/orgraphite); ketjen black; a graphitic carbon; a low dimensional carbon(e.g., carbon nanotubes); a carbon fiber; and/or the like.

Electrochemically inactive ceramic particles utilized in separatorlayers may comprise any suitable ceramic materials such as aluminumoxide (i.e., alumina (α-Al2O3)), corundum, calcined, tabular, syntheticboehmite, silicon oxides or silica, zirconia, and/or the like. In someexamples, the electrochemically inactive ceramic particles areelectrically non-conductive.

Binder mixtures utilized in the dry electrode mixes may comprise anysuitable material for use in dry electrode processing, such aspolytetrafluorethylene (PTFE); polyolefins such as polyvinylidenedifluoride (PVDF), polyethylene (PE), polypropylene (PP) polyethyleneoxide (PEO), and/or their mixtures or copolymers; steryl butadienerubber (SBR); polyacrylic acid; polyvinyl alcohol; carboxymethylcellulose; and/or the like. In some examples, the dry electrode mixturesinclude binder mixtures comprising a plurality of binders. Exemplarybinder mixtures include PTFE mixed with PVDF; PTFE mixed withco-polymers of PVDF, PTFE mixed with PEO; PTFE mixed with PP; and/or thelike.

In some examples, such as when the binder mixtures include one or morefibrilizable polymer materials (e.g., PTFE) and one or morenon-fibrilizable polymer materials (e.g., PVDF, PEO, PP), mixingelectrodes to form dry electrode mixes includes two or more mixingsteps. In some examples, a first mixing step includes mixing activematerial particles with non-fibrilizable polymer materials utilized inthe binder mixture to form an intermediate mixture. In some examples, asecond mixing step includes mixing the intermediate mixture withfibrilizable polymer materials utilized in the binder mixture. In someexamples, the second mixing step includes heating the dry electrodemixes to initiate fibrilization, networking, and/or the formation ofpolymer matrices between fibrilizable binder particles.

Step 204 of method 200 includes compressing individual electrodemixtures to form electrode films. Compressing the individual electrodemixes includes applying pressure to each electrode mix formed during theprevious step. In some examples, compressing the electrode mixesincludes pressing the electrode mixes between a pair of rollers, therebyforming electrode films. In some examples, rollers utilized to compressthe electrode mixes include raised, embossed, and/or engraved patternsdisposed on external surfaces, which may increase a surface roughness ofeach electrode film. Increasing a surface roughness of each electrodefilm may result in the production of interpenetrating boundarystructures (e.g., fingers, pores, etc.) at boundaries between electrodelayers. Interpenetrating boundary structures may increase a structuralintegrity of the electrode, may increase surface adhesion betweenelectrode layers, and may reduce interfacial resistance betweenelectrode layers. In some examples, one roller of the pair of rollersincludes patterns disposed on an external surface, and only one side ofthe electrode film has increased surface roughness. In some examples,both rollers of the pair of rollers include patterns disposed on anexternal surface, and both sides of the electrode film have increasedsurface roughness. In some examples, both rollers of the pair of rollershave smooth external surfaces, and both sides of the electrode film aresubstantially flat.

In some examples, compressing individual electrode mixtures to formelectrode films also includes compressing a current collector between apair of patterned rollers, thereby increasing a surface roughness of thecurrent collector. In some examples, increasing the surface roughness ofthe current collector increases an overall surface area of the currentcollector.

Step 206 of method 200 includes optionally heating the electrode films.Heating the electrode films includes applying heat to the compressedelectrode mixtures, thereby adhering the binder particles to each otherand to the electrode components included in the electrode mixes. In someexamples, rollers utilized in compressing the individual electrode mixesmay be heated, and the two steps may be performed simultaneously.Fibrilizable binder materials (e.g., PTFE) form networked polymermatrices when heated, which may trap electrode material particles suchas active material particles, carbon conductive particles, ceramicparticles, and/or the like within interstices of a polymer matrix.Non-fibrilizable binder materials (e.g., PVDF, PEO, PE, PP) may meltwhen heated, thereby adhering electrode material particles to eachother.

Step 208 of method 200 includes stacking the electrode films. Stackingthe electrode films includes determining an order of electrode layersincluded in the electrode and arranging the layers. The multilayeredsolventless electrode may include any suitable number of layers. In someexamples, the multilayered solventless electrode includes between twoand four layers. In some examples, a multilayered solventless electrodeincludes a first active material layer and a second active materiallayer. Stacking the electrode films therefore includes determining whichactive material layer is more suitable for inclusion in a top layer ofthe electrode (e.g., adjacent a separator) and which active materiallayer is suitable for inclusion in a bottom layer of the electrode(e.g., adjacent a current collector) and arranging the layers.

In some examples, a multilayered solventless electrode includes a firstactive material layer, a second active material layer, and a separatorlayer. Stacking the electrode films therefore includes determining whichactive material layer is more suitable for inclusion in a top activelayer of the electrode (e.g., adjacent the separator) and which activematerial layer is suitable for inclusion in a bottom active layer of theelectrode (e.g., adjacent a current collector) and arranging the layerssuch that the top active material layer is adjacent the separator layerand the bottom active material layer is adjacent the current collector.

In some examples, a multilayered solventless electrode includes a firstactive material layer, a second active material layer, a separatorlayer, and a carbon conductive layer. Stacking the electrode filmstherefore includes determining which active material layer is moresuitable for inclusion in a top active layer of the electrode (e.g.,adjacent the separator) and which active material layer is suitable forinclusion in a bottom active layer of the electrode (e.g., adjacent thecarbon conductive layer) and arranging the layers such that the topactive material layer is adjacent the separator layer and the bottomactive material layer is adjacent the carbon conductive layer, which isadjacent the current collector.

In some examples, stacking the electrode films includes increasingadhesion between electrode layers. In some examples, increasing adhesionbetween electrode layers includes applying a solvent spray and/oradhesive spray to one or more surfaces of each electrode layer. In someexamples, one or more binders included in binder mixtures are soluble,and spraying a small amount of solvent onto electrode film surfaces mayincrease adhesion between electrode layers. For example, PVDF is solublein n-methyl-2-pyrrolidone (NMP), acetone, tetrahydrofuran, methylenechloride, dimethylformamide, and/or cyclohexane. Co-polymers of PVDF mayalso be soluble in water, acetone, and/or other alcohols. Binders suchas steryl butadiene rubber (SBR), polyacrylic acid, polyvinyl alcohol,and mixtures including carboxymethyl cellulose are soluble in water, andmay be utilized in electrodes which are not sensitive to water.

In some examples, binders utilized in the binder mixtures are notsoluble in any solvent (e.g., PTFE). In these examples, other bindermaterials solvated in small amounts of solvent may be utilized in anadhesive spray (AKA glue spray). Electrode films including PTFE may besprayed with small amounts of PVDF solvated in NMP, which may adhere theelectrode layers without requiring a long drying time or complicatedsolvent-collection methods.

In some examples, increasing adhesion between electrode layers includesapplying a spray including a solvated conductive carbon material ontoelectrode film surfaces, which may both adhere layers and may fillinterstices and/or air gaps between adjacent layers. Suitable conductivecarbon materials may include nanometer-sized carbon (e.g., carbon blackand/or graphite); ketjen black; a graphitic carbon; a low dimensionalcarbon (e.g., carbon nanotubes); a carbon fiber; and/or the like.

In some examples, stacking the electrode films includes laminating abottom electrode layer to the current collector (e.g., using heating oradhesive). In some examples, stacking the electrode films includesheating the current collector using an external heater or a plurality ofheated rollers, thereby increasing adhesion with a bottom electrodelayer.

Step 210 of method 200 includes compressing the stacked electrode films.Compressing the stacked films includes applying pressure to stackedlayers simultaneously. In some examples, compressing the stacked filmsincludes utilizing a single pair of rollers to compress the electrodestack. In some examples, compressing the stacked films causesinterpenetrating boundary structures to form between adjacent layershaving increased surface roughness. Compressing the stacked films maycause the density of layers disposed adjacent to the current collectorto be higher than that of layers disposed further away from the currentcollector.

Step 212 of method 200 includes heating the compressed electrode stack.Heating the compressed electrode stack includes applying heat to thecompressed electrode films, thereby adhering the binder particles toeach other and to the electrode components included in the electrodemixes. In some examples, rollers utilized in compressing the electrodestack may be heated, and the two steps may be performed simultaneously.Fibrilizable binder materials (e.g., PTFE) form networked polymermatrices when heated, which may trap electrode material particles suchas active material particles, carbon conductive particles, ceramicparticles, and/or the like within interstices of a polymer matrix.Non-fibrilizable binder materials (e.g., PVDF, PEO, PE, PP) may meltwhen heated, thereby adhering adjacent electrode layers to each other.In some examples, the current collector may be heated to preferentiallyincrease the compressibility of the active material layer closest to thecurrent collector.

C. Illustrative Manufacturing System

Turning now to FIG. 3, an illustrative manufacturing system 300 for usewith method 200 will now be described. In some examples, a systemincluding a plurality of rollers configured to compress dry electrodemixes into electrode films and to compress stacks of electrode filmsinto electrodes may be used to manufacture multilayered solventlesselectrodes.

Manufacturing system 300 includes a first plurality of pairs of rollers310 configured to compress dry electrode mixes 314 comprisingparticulate into electrode films. Each roller 310 is mounted onto anaxle coupled to a pair of movable arms 312, which are configured tolaterally move the rollers 310. Laterally moving each pair of rollers310, either inward and outward may vary a density and a thickness of anelectrode film produced by each pair of rollers. In some examples, onlya single roller of each pair of rollers may be moveable. In use, eachpair of rollers 310 may be disposed a different distance apart, eachproducing an electrode film 324 having a different thickness. Rollers310 may be actuated by a motor, which rotates the rollers inward towarda dry electrode mix disposed between the rollers. In some examples, ahopper is utilized to pour pre-mixed dry electrode mixes into a spacebetween each pair of rollers. In some examples, rollers 310 are heated,and may initiate the formation of polymer matrices, lattices, and/ornetworks between binder particles included in electrode mixes. System300 may include any suitable number of pairs of rollers configured toproduce any suitable number of electrode layers.

A second pair of rollers 320 is configured to compress a stack ofelectrode films 324 produced using rollers 310 into a single electrodestack 326 including two multilayered electrodes with a current collectordisposed between the electrodes. Each roller of the pair of rollers 320is mounted onto an axle coupled to a pair of movable arms 322, which areconfigured to laterally move the rollers 320. Laterally moving each pairof rollers 320, either inward and outward may vary a density of thecompleted electrodes. Compressing stack 326 with the second pair ofrollers may cause electrode layers disposed closer to the currentcollector to have a higher density than rollers disposed further awayfrom the current collector. Rollers 320 may be actuated by a motor,which rotates the rollers inward toward the electrode stack disposedbetween the rollers. In some examples, rollers 310 are heated, and mayinitiate the formation of polymer matrices, lattices, and/or networksbetween binder particles of adjacent electrode films.

Rollers 310 and 320 may include patterns and/or structures configured toincrease a surface roughness of the electrode films and electrodes, suchas tooths, grooves, castellations, pins, and/or the like. FIGS. 4 and 5are schematic diagrams of pairs of rollers 400 and 500 suitable for usewith manufacturing system 300. In some examples, one roller 410 of apair of rollers 400 includes pattern 412, and a second roller 420 of thepair of rollers has a smooth external surface 422 (see FIG. 4). Pair ofrollers 400 may be suitable for use on outermost layers of theelectrode, producing surface adhesion between an outermost layer and anadjacent layer, while providing a smooth external electrode surface. Insome examples, both a first and a second roller 510, 520 of a pair ofrollers 500 include first and second patterns 512, 522 (see FIG. 5).Patterns and/or structures roughening adjacent layers need not match orinterlock, as roughened surfaces of electrode layers mesh, interlock,and/or form interpenetrating structures when compressed by rollers 320.

In some examples, system 300 includes a third pair of rollers 330, whichare configured to roughen a current collector 332. Rollers 330 may besubstantially identical to rollers 500, described above. Rougheningcurrent collector 322 may increase a total surface area and surfaceroughness of the current collector, which may increase adhesion betweenan adjacent electrode film and the current collector, and may increaseelectrical conductivity.

Current collector 322 may be transported through manufacturing system300 in a roll-to-roll process, which may pass the current collectorthrough rollers 330 and rollers 320. In some examples, current collector322 is heated by an optional heater 340 which may heat the currentcollector, further increasing electrode film adhesion. In some example,rollers 330 are heated and heater 340 is unnecessary.

In some examples, system 300 includes a plurality of sprayers 326,configured to spray a solvent or adhesive spray onto external surfacesof electrode films. In some examples, sprayers 326 are configured tospray a solvated carbon conductive material onto external surfaces ofthe electrode films, which may fill interstices between layers when theelectrode stack is compressed. In some examples, the plurality ofsprayers are configured to spray a solvated binder material ontoexternal surfaces, which may adhere adjacent layers.

D. First Illustrative Multilayered Solventless Electrode

As shown in FIG. 6, this section describes a first illustrativemultilayered solventless electrode 600 including a first active layer610 and a second active layer 620. First active layer 610 is disposed onand directly contacting a current collector 630, and includes aplurality of first active material particles mixed with a plurality offirst binder particles. Second active layer 620 is disposed on anddirectly contacting first layer 620, and includes a plurality of secondactive material particles mixed with a plurality of second binderparticles. An electrolyte may be disposed throughout the electrode.First active layer 610 and second active layer 620 are examples ofelectrode films manufactured as described in method 200.

In some examples, electrode 600 is an anode, and the first and secondactive material particles comprise any suitable anode material orcombination of anode materials, such as graphite (artificial ornatural), hard carbon, titanate, titania, transition metals in general,elements in group 14 (e.g., carbon, silicon, tin, germanium, etc.),oxides, sulfides, transition metals, halides, chalcogenides, and/or thelike. In some examples, electrode 600 is a cathode, and the first andsecond active material particles comprise any suitable cathode materialor combination of cathode materials, such as transition metals (forexample, nickel, cobalt, manganese, copper, zinc, vanadium, chromium,iron), and their oxides, phosphates, phosphites, silicates, alkalinesand alkaline earth metals, aluminum, aluminum oxides and aluminumphosphates, halides, chalcogenides, and/or the like. In some examples,the first active material particles and the second active materialparticles comprise different active materials. In some examples, thefirst active material particles and the second active material particlescomprise active material particles having different particle shapesand/or sizes.

The first and second binder mixture may comprise any suitable materialfor use in dry electrode processing, such as polytetrafluorethylene(PTFE); polyolefins such as polyvinylidene difluoride (PVDF),polyethylene (PE), polypropylene (PP) polyethylene oxide (PEO), and/ortheir mixtures or copolymers; steryl butadiene rubber (SBR); polyacrylicacid; polyvinyl alcohol; carboxymethyl cellulose; and/or the like. Insome examples, the dry electrode mixtures include binder mixturescomprising a plurality of binders. Exemplary binder mixtures includePTFE mixed with PVDF; PTFE mixed with co-polymers of PVDF, PTFE mixedwith PEO; PTFE mixed with PP; and/or the like.

Binder mixtures may include any suitable ratio of binder materials. Forexample, binder mixtures may include PTFE mixed with PVDF in a ratiofrom 1:3 to 3:1. In some examples, binder mixtures include PTFE mixedwith any suitable non-fibrilizing binder material in a ratio from 1:3 to3:1. In some examples, binder mixtures include between 20% and 98% PTFEby weight.

In some examples, one or both of first active layer 610 and secondactive layer 620 include conductive additives, such as nanometer-sizedcarbon (e.g., carbon black and/or graphite); ketjen black; a graphiticcarbon; a low dimensional carbon (e.g., carbon nanotubes); a carbonfiber; and/or the like. First active layer 610 and second active layer620 may include any suitable mixtures of active material components. Insome examples, first active layer 610 includes 70% to 99% activematerial particles by weight, 1% to 20% binder particles by weight, and1% to 10% carbon conductive material by weight. In some examples, secondactive layer 620 includes 70% to 99% active material particles byweight, 1% to 20% binder particles by weight, and 1% to 10% carbonconductive material by weight.

In examples wherein a binder mixture includes PTFE, active materialparticles and carbon conductive particles included in the respectiveelectrode layer are disposed within interstices formed within afibrilized polymer matrix formed by the PTFE. In examples wherein abinder mixture includes a polyolefin material, such as PVDF, PEO, PE,PP, and/or the like, the polyolefin may melt and encapsulate activematerial particles and carbon conductive particles in a matrix formed bythe melted polyolefin material.

E. Second Illustrative Multilayered Solventless Electrode

As shown in FIG. 7, this section describes a second illustrativemultilayered solventless electrode 700 including a carbon conductivelayer 730, a first active layer 710, and a second active layer 720.Carbon conductive layer 730 is disposed on and directly contacting acurrent collector 740, and includes a plurality of carbon conductiveparticles mixed with a plurality of third binder particles. First activelayer 710 is disposed on and directly contacting carbon conductive layer730 and includes a plurality of first active material particles mixedwith a plurality of first binder particles. Second active layer 720 isdisposed on and directly contacting first active layer 710, and includesa plurality of second active material particles mixed with a pluralityof second binder particles. An electrolyte may be disposed throughoutthe electrode. First active layer 710, second active layer 720, andcarbon conductive layer 730 are examples of electrode films manufacturedas described in method 200. Electrode 700 may be substantially identicalto electrode 600, except as described below.

Carbon conductive layer 730 may improve electrical conductivity betweenfirst active layer 710 and current collector 740. In some examples,carbon conductive layer 730 insulates the current collector from heatgenerated by the active layers.

The carbon conductive particles may comprise any suitable carbon-basedmaterial configured to increase electrical conductivity between activematerial layers and the current collector, such as nanometer-sizedcarbon (e.g., carbon black and/or graphite); ketjen black; a graphiticcarbon; a low dimensional carbon (e.g., carbon nanotubes); a carbonfiber; and/or the like.

The third binder mixture may comprise any suitable material for use indry electrode processing, such as polytetrafluorethylene (PTFE);polyolefins such as polyvinylidene difluoride (PVDF), polyethylene (PE),polypropylene (PP) polyethylene oxide (PEO), and/or their mixtures orcopolymers; steryl butadiene rubber (SBR); polyacrylic acid; polyvinylalcohol; carboxymethyl cellulose; and/or the like. In some examples, thedry electrode mixtures include binder mixtures comprising a plurality ofbinders. Exemplary binder mixtures include PTFE mixed with PVDF; PTFEmixed with co-polymers of PVDF, PTFE mixed with PEO; PTFE mixed with PP;and/or the like.

Binder mixtures may include any suitable ratio of binder materials. Forexample, binder mixtures may include PTFE mixed with PVDF in a ratiofrom 1:3 to 3:1. In some examples, binder mixtures include PTFE mixedwith any suitable non-fibrilizing binder material in a ratio from 1:3 to3:1. In some examples, binder mixtures include between 20% and 98% PTFEby weight.

Carbon conductive layer 730 may include any suitable mixtures of carbonconductive particles and binder particles. In some examples, carbonconductive layer 730 includes 50% to 95% carbon conductive particles byweight, and 1% to 50% binder particles by weight.

In examples wherein a binder mixture includes PTFE, carbon conductiveparticles included in the respective electrode layer are disposed withininterstices formed within a fibrilized polymer matrix formed by thePTFE. In examples wherein a binder mixture includes a polyolefinmaterial, such as PVDF, PEO, PE, PP, and/or the like, the polyolefin maymelt and encapsulate carbon conductive particles in a matrix formed bythe melted polyolefin material.

F. Third Illustrative Multilayered Solventless Electrode

As shown in FIG. 8, this section describes a third illustrativemultilayered solventless electrode 800 including a carbon conductivelayer 830, a first active layer 810, a second active layer 820, and anintegrated separator layer 840. Carbon conductive layer 830 is disposedon and directly contacting a current collector 850, and includes aplurality of carbon conductive particles mixed with a plurality of thirdbinder particles. First active layer 810 is disposed on and directlycontacting carbon conductive layer 830, and includes a plurality offirst active material particles mixed with a plurality of first binderparticles. Second active layer 820 is disposed on and directlycontacting first active layer 810, and includes a plurality of secondactive material particles mixed with a plurality of second binderparticles. Integrated separator layer 840 is disposed on and directlycontacting second active layer 820, and includes a plurality ofelectrochemically inactive ceramic particles mixed with a plurality offourth binder particles. An electrolyte may be disposed throughout theelectrode. First active layer 810, second active layer 820, carbonconductive layer 830, and integrated separator layer 840 are examples ofelectrode films manufactured as described in method 200. Electrode 800may be substantially identical to electrode 700, except as describedbelow.

Separator layer 840 may be configured such that the separator isolatesthe electrode (e.g., anode or cathode) from an adjacent electrodeincluded within an electrochemical cell, while maintaining permeabilityto a charge carrier such as a lithium-ion containing electrolyte. Insome embodiments, the electrochemically inactive particles compriseceramics such as aluminum oxide (i.e., alumina (α-Al₂O₃)), corundum,calcined, tabular, synthetic boehmite, silicon oxides or silica,zirconia, and/or the like. In some examples, the electrochemicallyinactive particles are electrically non-conductive.

The fourth binder mixture may comprise any suitable material for use indry electrode processing, such as polytetrafluorethylene (PTFE);polyolefins such as polyvinylidene difluoride (PVDF), polyethylene (PE),polypropylene (PP) polyethylene oxide (PEO), and/or their mixtures orcopolymers; steryl butadiene rubber (SBR); polyacrylic acid; polyvinylalcohol; carboxymethyl cellulose; and/or the like. In some examples, thedry electrode mixtures include binder mixtures comprising a plurality ofbinders. Exemplary binder mixtures include PTFE mixed with PVDF; PTFEmixed with co-polymers of PVDF, PTFE mixed with PEO; PTFE mixed with PP;and/or the like.

Binder mixtures may include any suitable ratio of binder materials. Forexample, binder mixtures may include PTFE mixed with PVDF in a ratiofrom 1:3 to 3:1. In some examples, binder mixtures include PTFE mixedwith any suitable non-fibrilizing binder material in a ratio from 1:3 to3:1. In some examples, binder mixtures include between 20% and 98% PTFEby weight.

Integrated separator layer 840 may include any suitable mixtures ofelectrochemically inactive ceramic particles and binder particles. Insome examples, integrated separator layer 840 includes 50% and 99%electrochemically inactive ceramic particles by weight, and 1% to 50%binder particles by weight. In some examples, integrated separator layer840 includes greater than 99% electrochemically inactive ceramicparticles by weight, and less than 1% binder particles by weight. Insome examples, integrated separator layer 840 includes less than 50%electrochemically inactive ceramic particles by weight, and greater than50% binder particles by weight.

In examples wherein a binder mixture includes PTFE, electrochemicallyinactive ceramic particles included in the respective electrode layerare disposed within interstices formed within a fibrilized polymermatrix formed by the PTFE. In examples wherein a binder mixture includesa polyolefin material, such as PVDF, PEO, PE, PP, and/or the like, thepolyolefin may melt and encapsulate electrochemically inactive ceramicparticles in a matrix formed by the melted polyolefin material.

G. First Illustrative Multilayered Solventless Electrode Stack

As shown in FIG. 9, this section describes a first illustrativemultilayered solventless electrode stack 900 including a carbonconductive layer 930, a first active layer 910, and a second activelayer 920. Carbon conductive layer 930 is disposed on and directlycontacting a current collector 940, and includes a plurality of carbonconductive particles mixed with a plurality of third binder particles.First active layer 910 is disposed on and directly contacting carbonconductive layer 930 and includes a plurality of first active materialparticles mixed with a plurality of first binder particles. Secondactive layer 920 is disposed on and directly contacting first activelayer 910, and includes a plurality of second active material particlesmixed with a plurality of second binder particles. An electrolyte may bedisposed throughout the electrode. First active layer 910, second activelayer 920, and carbon conductive layer 930 are examples of electrodefilms manufactured as described in method 200. Electrode 900 may besubstantially identical to electrode 700, except as described below.

FIG. 9 depicts a stack of roughened electrode films, as described inmethod 200. The roughened electrode films depicted in FIG. 9 forminterpenetrating electrode structures when calendered as an electrodestack, as described with respect to step 208 of method 200. Eachelectrode film surface includes a plurality of protrusions,castellations, fingers, and/or the like, which result from manufacturingan electrode film utilizing patterned rollers. First active layer 910and carbon conductive layer 930 are manufactured using rollers 500, asdescribed above. First active layer 910 and carbon conductive layer 930include roughened surfaces 912, 932 disposed on both sides of theelectrode layer. In contrast, second active layer 920 is manufacturedusing rollers 400, as described above. Second active layer 920 includesone roughened internal surface 922 and one smooth external surface 924.As electrode 900 does not include an integrated ceramic separator,external surface 924 is configured to interface with a polyolefin (e.g.,polyethylene, polypropylene, etc.) separator disposed on the externalsurface. Current collector 940 also includes roughened surfaces 942,which increase adhesion with conductive layer 930 when calendered.

In some examples, roughened surfaces 912, 932, 922 have a tailoredsurface roughness. In some examples, roughened surfaces 912, 932, 922have a maximum-minimum differential (e.g., between peaks and valleys)from 0.5 μm to 10 μm.

In response to calendering, the roughened surfaces depicted in FIG. 9will create interpenetrating boundary structures configured to decreaseinterfacial resistance between the layers, reduce lithium plating, andincrease adhesion between the layers. An interlocking region will bedisposed between respective roughened, layers, comprising a non-planarboundary between layers. In some examples, each layer may includerespective, three-dimensional, interpenetrating structures,interchangeably referred to as protrusions, castellations, extensions,projections, fingers, and/or the like locking adjacent layers together,forming a mechanically robust interface that is capable of withstandingstresses, such as those due to electrode expansion and compression.Additionally, the non-planar surfaces defined by the fingers representan increased total surface area of the interface boundary, which mayprovide increased interfacial resistance and may increase ion mobilitythrough the electrode. The relationship between the fingers may bedescribed as interlocking, interpenetrating, intermeshing,interdigitating, interconnecting, interlinking, and/or the like.

When particles of the electrode formed from electrode stack 900 arelithiating or delithiating, the electrode remains coherent, and thebottom layer and the top layer remain bound by the interlocking region.In general, the interdigitation or interpenetration of fingers, as wellas the increased surface area of the interphase boundary, function toadhere the two zones together.

During charging and discharging of the battery, active materialparticles may contract and expand, causing the layers to contract andswell. During swelling and contracting, the electrode may remaincoherent, and electrode layers may remain bound by the interlockingregion. This bonding of the layers may decrease interfacial resistancebetween the layers and maintain mechanical integrity of anelectrochemical cell including the electrode.

H. Second Illustrative Multilayered Solventless Electrode Stack

As shown in FIG. 10, this section describes a second illustrativemultilayered solventless electrode stack 1000 including a carbonconductive layer 1030, a first active layer 1010, a second active layer1020, and an integrated separator layer 1040. Carbon conductive layer1030 is disposed on and directly contacting a current collector 1050,and includes a plurality of carbon conductive particles mixed with aplurality of third binder particles. First active layer 1010 is disposedon and directly contacting carbon conductive layer 1030, and includes aplurality of first active material particles mixed with a plurality offirst binder particles. Second active layer 1020 is disposed on anddirectly contacting first active layer 1010, and includes a plurality ofsecond active material particles mixed with a plurality of second binderparticles. Integrated separator layer 1040 is disposed on and directlycontacting second active layer 1020, and includes a plurality ofelectrochemically inactive ceramic particles mixed with a plurality offourth binder particles. An electrolyte may be disposed throughout theelectrode. First active layer 1010, second active layer 1020, carbonconductive layer 1030, and integrated separator layer 1040 are examplesof electrode films manufactured as described in method 200. Electrode1000 may be substantially identical to electrode 800, except asdescribed below.

FIG. 10 depicts a stack of roughened electrode films, as described inmethod 200. The roughened electrode films depicted in FIG. 10 forminterpenetrating electrode structures when calendered as an electrodestack, as described with respect to step 208 of method 200. Eachelectrode film surface includes a plurality of protrusions,castellations, fingers, and/or the like, which result from manufacturingan electrode film utilizing patterned rollers. First active layer 1010,second active layer 1020, and carbon conductive layer 1030 aremanufactured using rollers 500, as described above. First active layer1010, second active layer 1020, and carbon conductive layer 1030 includeroughened surfaces 1012, 1022, and 1032 disposed on both sides of theelectrode layer. In contrast, integrated ceramic separator layer 1040 ismanufactured using rollers 400, as described above. Integrated ceramicseparator layer 1040 includes one roughened internal surface 1042 andone smooth external surface 1044. External surface 1044 is configured tointerface with a polyolefin (e.g., polyethylene, polypropylene)separator disposed on the external surface, or with an adjacentintegrated ceramic separator of another electrode. Current collector1050 also includes roughened surfaces 1052, which increase adhesion withconductive layer 1052 when calendered.

In some examples, roughened surfaces 1012, 1022, 1032, 1042 have atailored surface roughness. In some examples, roughened surfaces 1012,1022, 1032, 1042 have a maximum-minimum differential (e.g., betweenpeaks and valleys) from 0.5 μm to 10 μm.

In response to calendering, the roughened surfaces depicted in FIG. 10will create interpenetrating boundary structures configured to decreaseinterfacial resistance between the layers, reduce lithium plating, andincrease adhesion between the layers. An interlocking region will bedisposed between respective roughened, layers, comprising a non-planarboundary between layers. In some examples, each layer may includerespective, three-dimensional, interpenetrating structures,interchangeably referred to as protrusions, castellations, extensions,projections, fingers, and/or the like locking adjacent layers together,forming a mechanically robust interface that is capable of withstandingstresses, such as those due to electrode expansion and compression.Additionally, the non-planar surfaces defined by the fingers representan increased total surface area of the interface boundary, which mayprovide increased interfacial resistance and may increase ion mobilitythrough the electrode. The relationship between the fingers may bedescribed as interlocking, interpenetrating, intermeshing,interdigitating, interconnecting, interlinking, and/or the like.

When particles of the electrode formed from electrode stack 1000 arelithiating or delithiating, the electrode remains coherent, and thebottom layer and the top layer remain bound by the interlocking region.In general, the interdigitation or interpenetration of fingers, as wellas the increased surface area of the interphase boundary, function toadhere the two zones together.

During charging and discharging of the battery, active materialparticles may contract and expand, causing the layers to contract andswell. During swelling and contracting, the electrode may remaincoherent, and electrode layers may remain bound by the interlockingregion. This bonding of the layers may decrease interfacial resistancebetween the layers and maintain mechanical integrity of anelectrochemical cell including the electrode.

I. Illustrative Combinations and Additional Examples

This section describes additional aspects and features of solventlessmultilayered electrodes, presented without limitation as a series ofparagraphs, some or all of which may be alphanumerically designated forclarity and efficiency. Each of these paragraphs can be combined withone or more other paragraphs, and/or with disclosure from elsewhere inthis application, including the materials incorporated by reference inthe Cross-References, in any suitable manner. Some of the paragraphsbelow expressly refer to and further limit other paragraphs, providingwithout limitation examples of some of the suitable combinations.

A0. A method for manufacturing a solventless electrode, the methodcomprising:

mixing a plurality of electrode particles to form a plurality of dryelectrode mixtures;

compressing each electrode mixture of the plurality of dry electrodemixtures to form a plurality of electrode films;

stacking the electrode films; and

compressing the stacked electrode films.

A1. The method of paragraph A0, further comprising heating the electrodefilms.

A2. The method of paragraph A0 or A1, further comprising heating thestacked electrode films.

A3. The method of any of paragraphs A0 through A2, wherein the dryelectrode mixtures include a first dry electrode mixture comprising aplurality of first active material particles and a first binder mixture,and a second dry electrode mixture comprising a plurality of secondactive material particles and a second binder mixture.

A4. The method of paragraph A3, wherein the dry electrode mixturesfurther include a third dry electrode mixture comprising a plurality ofelectrically conductive carbon particles and a third binder mixture.

A5. The method of paragraph A3 or A4, wherein the dry electrode mixturesfurther include a fourth dry electrode mixture comprising a plurality ofnon-active ceramic particles and a fourth binder mixture.

A6. The method of any of paragraphs A3 through A5, wherein thesolventless electrode is an anode.

A7. The method of any of paragraphs A3 through A5, wherein thesolventless electrode is a cathode.

A8. The method of any of paragraphs A3 through A7, wherein each of thebinder mixtures comprises a mixture of polytetrafluorethylene and apolyolefin.

A9. The method of paragraph A8, wherein the polyolefin comprisespolyvinylidene difluoride.

A10. The method of any of paragraphs A0 through A9, wherein compressingeach electrode mixture includes pressing the electrode mixture between apair of rollers.

A11. The method of paragraph A10, wherein at least one roller of thepair of rollers includes a pattern disposed on an external surface,wherein the at least one roller is configured to increase a surfaceroughness of an electrode film compressed between the pair of rollers.

A12. The method of any of paragraphs A0 through A11, wherein stackingthe electrode films includes determining an order of electrode layersincluded in the electrode and arranging the layers.

A13. The method of any of paragraphs A0 through A12, further includingincreasing adhesion between the electrode films.

A14. The method of paragraph A13, wherein increasing adhesion betweenthe electrode films further includes applying a solvent spray to one ormore surfaces of each electrode film.

A15. The method of paragraph A13, wherein increasing adhesion betweenthe electrode films further includes applying an adhesive spraycomprising binder molecules solvated in small amounts of solvent to oneor more surfaces of each electrode film.

A16. The method of paragraph A13, wherein increasing adhesion betweenthe electrode films further includes applying a spray including asolvated conductive carbon material to one or more surfaces of eachelectrode film.

A17. The method of any of paragraphs A0 through A16, wherein compressingthe stacked electrode films includes pressing the stacked electrodefilms between a pair of rollers.

B0. A system for manufacturing solventless electrodes, the systemcomprising:

a first plurality of rollers configured to compress dry electrodemixtures comprising particulate into electrode films; and

a second pair of rollers configured to compress a stack of electrodefilms into a single electrode stack.

B1. The system of paragraph B0, wherein at least one roller of the firstplurality of rollers includes patterns disposed on an exterior surfaceconfigured to increase a surface roughness of the electrode films.

B2. The system of paragraph B0 or B1, further including a third pair ofrollers having patterns disposed on an exterior surface, the patternsconfigured to increase a surface roughness of a current collector.

B3. The system of any of paragraphs B0 through B2, further comprising aheater.

B4. The system of any of paragraphs B0 through B3, further comprising aplurality of sprayers configured to spray a solvent or adhesive ontosurfaces of the electrode films.

C0. An electrode for an electrochemical cell comprising:

a current collector substrate;

a first active material layer layered onto the current collectorsubstrate, the first active material layer comprising a first electrodefilm including a first plurality of active material particles adheredtogether by a first binder mixture; and

a second active material layer layered onto the first active materiallayer, the second active material layer comprising a second electrodefilm including a second plurality of active material particles adheredtogether by a second binder mixture;

wherein the first electrode film and the second electrode film includeactive material particles encapsulated in a polymer matrix formed by thebinder mixture.

C1. The electrode of paragraph C0, further comprising a carbonconductive layer disposed between the current collector substrate andthe first active material layer, the carbon conductive layer comprisinga third electrode film including a plurality of conductive carbonparticles adhered together by a third binder mixture.

C2. The electrode of paragraph C0 or C1, further comprising anintegrated separator layer layered onto the second active materiallayer, the integrated separator layer comprising a plurality ofnon-active ceramic particles adhered together by a fourth bindermixture.

C3. The electrode of any of paragraphs C0 through C2, wherein each ofthe binder mixtures comprises a mixture of polytetrafluorethylene and apolyolefin.

C4. The method of paragraph C3, wherein the polyolefin comprisespolyvinylidene difluoride.

D0. A method for manufacturing a solventless electrode, the methodcomprising:

mixing a first plurality of active material particles with a firstbinder to form a first dry electrode mixture;

mixing a second plurality of active material particles with a secondbinder to form a second dry electrode mixture;

compressing the first dry electrode mixture to form a first electrodefilm;

compressing the second dry electrode mixture to form a second electrodefilm;

stacking the first electrode film onto a current collector and thesecond electrode film onto the first electrode film; and

compressing the stacked electrode films.

D1. The method of paragraph D0, further comprising heating the firstelectrode film and the second electrode film, thereby adhering thebinders and the active material particles together.

D2. The method of paragraph D0 or D1, further comprising heating thestacked electrode films, thereby adhering the electrode films to eachother.

D3. The method of any of paragraphs D0 through D2, further comprising:

mixing a first plurality of electrically conductive carbon particleswith a third binder to form a third dry electrode mixture;

compressing the third dry electrode mixture to form a third electrodefilm; and

stacking the third electrode film between the current collector and thefirst electrode film.

D4. The method of any of paragraphs D0 through D3, further comprising:

mixing a first plurality of electrochemically inactive ceramic particleswith a fourth binder to form a fourth dry electrode mixture;

compressing the fourth dry electrode mixture to form a fourth electrodefilm; and

stacking the fourth electrode film onto the second electrode film.

D5. The method of any of paragraphs D0 through D4, wherein the firstbinder and the second binder each comprise a mixture ofpolytetrafluoroethylene and a polyolefin.

D6. The method of paragraph D5, wherein the polyolefin comprisespolyvinylidene difluoride.

D7. The method of any of paragraphs D0 through D6, wherein compressingthe first dry electrode mixture and the second dry electrode mixtureincludes pressing each electrode mixture between a pair of rollers.

D8. The method of paragraph D7, wherein at least one roller of the pairof rollers includes a pattern disposed on an external surface, whereinthe at least one roller is configured to increase a surface roughness ofan electrode film compressed between the pair of rollers.

D9. The method of any of paragraphs D0 through D8, further includingincreasing adhesion between the electrode films.

D10. The method of paragraph D9, wherein increasing adhesion between theelectrode films further includes applying a solvent spray to one or moresurfaces of each electrode film.

D11. The method of paragraph D9, wherein increasing adhesion between theelectrode films further includes applying an adhesive spray comprisingbinder molecules solvated in small amounts of solvent to one or moresurfaces of each electrode film.

D12. The method of paragraph D9, wherein increasing adhesion between theelectrode films further includes applying a spray including a solvatedconductive carbon material to one or more surfaces of each electrodefilm.

D13. The method of any of paragraphs D0 through D12, wherein compressingthe stacked electrode films includes pressing the stacked electrodefilms between a pair of rollers.

Advantages, Features, and Benefits

The different embodiments and examples of the multilayered solventlesselectrodes described herein provide several advantages over knownsolutions for manufacturing electrodes for Li-ion electrochemical cells.For example, illustrative embodiments and examples described hereinreduce the use of expensive and environmentally toxic solvents.

Additionally, and among other benefits, illustrative embodiments andexamples described herein allow for the use of multiple active materialsin different layers of a solventless electrode, thereby improvingelectrochemical properties of the electrode.

Additionally, and among other benefits, illustrative embodiments andexamples described herein improve surface adhesion between electrodelayers manufactured using dry manufacturing techniques.

Additionally, and among other benefits, illustrative embodiments andexamples described herein reduce manufacturing time of electrodes andelectrochemical cells by eliminating any drying steps.

Additionally, and among other benefits, illustrative embodiments andexamples described herein allow increased control over layer features,including thickness, density, and surface roughness.

No known system or device can perform these functions. However, not allembodiments and examples described herein provide the same advantages orthe same degree of advantage.

CONCLUSION

The disclosure set forth above may encompass multiple distinct exampleswith independent utility. Although each of these has been disclosed inits preferred form(s), the specific embodiments thereof as disclosed andillustrated herein are not to be considered in a limiting sense, becausenumerous variations are possible. To the extent that section headingsare used within this disclosure, such headings are for organizationalpurposes only. The subject matter of the disclosure includes all noveland nonobvious combinations and subcombinations of the various elements,features, functions, and/or properties disclosed herein. The followingclaims particularly point out certain combinations and subcombinationsregarded as novel and nonobvious. Other combinations and subcombinationsof features, functions, elements, and/or properties may be claimed inapplications claiming priority from this or a related application. Suchclaims, whether broader, narrower, equal, or different in scope to theoriginal claims, also are regarded as included within the subject matterof the present disclosure.

What is claimed is:
 1. A system for solventless manufacturing ofelectrodes, the system comprising: a plurality of first pairs of rollersconfigured to compress dry electrode mixtures comprising particulateinto stand-alone electrode films; a hopper configured to pour the dryelectrode mixtures into a space between each of the first pairs ofrollers; and a second pair of rollers configured to compress a stack ofstand-alone electrode films into a single electrode stack.
 2. The systemof claim 1, wherein at least one roller of each pair of rollers includespatterns disposed on an exterior surface configured to increase asurface roughness of the stand-alone electrode films.
 3. The system ofclaim 1, further including a third pair of rollers having patternsdisposed on an exterior surface, the patterns configured to increase asurface roughness of a current collector.
 4. The system of claim 1,further comprising a heater configured to heat a current collector. 5.The system of claim 1, further comprising a plurality of sprayersconfigured to spray a solvent or adhesive onto surfaces of thestand-alone electrode films.
 6. The system of claim 1, wherein a firstroller of each of the first pairs of rollers is coupled to a movablearm, which is configured to laterally move the roller such that athickness of the stand-alone electrode films is varied.
 7. The system ofclaim 1, wherein each roller of the first pairs of rollers is heated,such that the heated rollers are configured to cause polymer matrices toform between binder particles included in the dry electrode mixtures. 8.The system of claim 1, further comprising a plurality of sprayersconfigure to spray an adhesive spray onto external surfaces of thestand-alone electrode films.
 9. The system of claim 8, wherein theadhesive spray comprises a solvated binder material.
 10. An electrodefor an electrochemical cell comprising: a current collector substrate; afirst active material layer layered onto the current collectorsubstrate, the first active material layer comprising a firststand-alone electrode film including a plurality of first activematerial particles adhered together by a first binder mixture; and asecond active material layer layered onto the first active materiallayer, the second active material layer comprising a second stand-aloneelectrode film including a plurality of second active material particlesadhered together by a second binder mixture; wherein the first activematerial particles are encapsulated in a polymer matrix formed by thefirst binder mixture and the second active material particles areencapsulated in a polymer matrix formed by the second binder mixture.11. The electrode of claim 10, further comprising a carbon conductivelayer disposed between the current collector substrate and the firstactive material layer, the carbon conductive layer comprising a thirdstand-alone electrode film including a plurality of conductive carbonparticles adhered together by a third binder mixture.
 12. The electrodeof claim 11, further comprising an integrated separator layer layeredonto the second active material layer, the integrated separator layercomprising a plurality of electrochemically inactive ceramic particlesadhered together by a fourth binder mixture.
 13. The electrode of claim11, wherein each of the first and second binder mixtures comprises amixture of polytetrafluorethylene and a polyolefin.
 14. The electrode ofclaim 13, wherein the polyolefin comprises polyvinylidene difluoride.15. A solventless method for manufacturing an electrode, the methodcomprising: compressing a first dry electrode mixture between a firstpair of rollers to form a first standalone electrode film, wherein afirst roller of the first pair of rollers includes a pattern disposed onan external surface; increasing a surface roughness of a first surfaceof the first standalone electrode film using the first roller of thefirst pair of rollers; compressing a second dry electrode mixturebetween a second pair of rollers to form a second standalone electrodefilm, wherein a second roller of the second pair of rollers includes apattern disposed on an external surface; increasing a surface roughnessof a second surface of the second standalone electrode film using thesecond roller of the second pair of rollers; stacking the firststandalone electrode film onto a current collector; stacking the secondstandalone electrode film onto the first standalone electrode film, suchthat the first surface of the first standalone electrode film isadjacent to the second surface of the second standalone electrode film;and compressing the stacked electrode films such that interpenetratingboundary structures form between the first standalone electrode film andthe second standalone electrode film.
 16. The method of claim 15,wherein the first dry electrode mixture comprises a first plurality ofactive material particles and a first binder mixture.
 17. The method ofclaim 16, wherein the second dry electrode mixture comprises a secondplurality of active material particles and a second binder mixture. 18.The method of claim 16, wherein the second dry electrode mixturecomprises a plurality of electrochemically inactive ceramic particlesand a second binder.
 19. The method of claim 16, wherein the firstbinder mixture comprises a fibrilizable polymer material mixed with anon-fibrilizable polymer material.
 20. The method of claim 19, whereinthe fibrilizable polymer material comprises polytetrafluorethylene, andwherein the non-fibrilizable polymer material comprises a polyolefin.